The prior art includes methods for selective carborization and heat treatment of iron based material during the hardening processes. Such a method is, for example, described in the Swedish Patent No. 8400781 to D. B. Larsen, issued Feb. 27, 1986. In accordance with the method of this patent selective carburization is obtained by selectively covering the substrate with an electro deposited copper alloy layer. If the copper layer is sufficiently deep, no carburization will occur beneath the layer.
However, the carbon content present prior to the application of the copper layer will still be there. Any residual carbon content reduces the magnetic permeability.